Manufacture of rayon



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Patented July 5, 1932 UNITED ST TE PATENT OFFICE enonen n. LOGKHAB'I', or rnovmsnon, BHODE Ismuvn, ASSIGNOR 'ro MANVILLE muons 00mm, or PAWTUCKET, RHODE ISLAND, a conrom'rron or RHODE ISLAND I MANUFACTURE OF IRAYON Ho Drawing.

The invention relates to the manufacture of rayon (artificial silk) and more particularly to the production of dyed rayon thread formed under the viscose process.

The present invention has for its object to produce from a viscose solution lustrous thread of high tensile strength which is dyed to its final color upon being precipitated in the setting bath.

in the manufacture of rayon or artificial si from a viscose solution as usuall carried out, the viscose is precipitated 1n the form of slender filaments by forcing the viscose solution through a spinneret into a precipitating or setting bath. The filaments are then athered together to form a thread and the i-read is either wound on a bobbin or guided to a centrifuge pot by which it is twisted and formed into a so-called cake. From the bobbin or cake as the case may he, the thread is wound on reels to form skeins which are then subjected to a series of operations to prepare the rayon for commercial use. These operations include washing, stretching, drying, desulphurizing, bleaching, dyeing, etc. The rayon is then finally spooled and is ready for commercial use.

The results produced by the usual methods of dyeing rayon thread in skein form, however, are not entirely satisfactory. Not only is the operation expensive on account of the high cost of labor, materials, and apparatus, but what is of more importance, the cellulose of which the thread is composed does not dye readily or uniformly in all cases, variations in color being produced for various reasons, as for instance, where portions of the thread have been converted from hydrocellulose into oxycellulose during the drying operation, or where the thread is not of uniform thickness, or where all portions of the skein .have not been subjected to the same amount 'Appllcation filed November 9, i988. Serial No. 818,808.

which has been once produced, with any degree of accuracy.

It is the object of the resent invention to rovide a method for yeing rayon made rom viscose which will avoid these objections and provide a uniformly dyed thread the color of which may be determined with mathematical accuracy.

With this object in view, the applicant proposes to insert the dyestuff in the viscose solution so that when the viscose is forced through the s innerets into the coagulating bath, viscose laments will be produced having the desired color and requiring no further treatment so far as the dyeing operation is concerned. So far as the applicant is aware, no one up to the present time has suc cessfully dyed rayon made from viscose in the viscose solution, so that the filaments duced from the setting bath are in their dyed state. Applicants experiments, for instance, have indicated that it is impracticable to put direct dyes or pigments into the viscose solution, inasmuch as these substances tend either to materially weaken the thread produced or make the viscose entirely unsuitable to be drawn out into filaments through the spinnerets. Similarly, where the applicant has attempted to use indanthrene or sulphur dyes, mixing. them in the usual manner with a reducing agent to render them soluble, and then adding them to the viscose solution, the tendency has been to stabilize the viscose solution and prevent proper aging and obtaining the right viscosity for spinning the viscose.

In carryin out the present method for successfully yeing in the viscose solution, the applicant employs dyes which must be put into a state of reduction-to render them soluble of which examples are indanthrene and sulphur colors, and these dyes are put and held in a reduced state by the w'scose solution until after the viscose has been forced through the spinnerets into the setting bath, and are then fixed in the newly formed viscose filaments to roduce the required color. For reducing and holding the dye in a reduced state, the chemicals are utilized which are formed in the process of viscose manufaczanthate, a definite amount of 3% caustic well mixed in the solution.

solution is required as will be readily understood by those skilled in the art. Some of this 3% caustic solution is taken and mixed with the dye to make it into a paste and the remainder of the caustic solution is added to the zanthate. added to the viscose in the dissolving machine. B the usual mechanical methods of stirring, t e viscose becomes thoroughly dissolved while at the same time the dyestufi is The viscose solution serves as a reducing agent for the dye and holds it permanently in a reduced state during the subsequent aging and until it reaches the settin bath.

The setting bat may be that usually employed in the viscose process of producing rayon, i. e., sulphuric acid and sodium sulphate, and acts as an oxidizing agent for the gyefitufi as the filaments are formed inthe At the same time that the viscose is drawn from the spinnerets into filaments in the setting bath, the dyestufi in the precipitated viscose becomes oxidized and is fixed in the substance of the filaments to give the thread its final color. Due to the method here employed of mixing the dyestufi' thoroughly lnto the viscose solution and holding it in a reduced state until the viscose is precipitated in the setting bath, an even distribution of the coloringmatter is secured, as filaments are roduced, to insure a constant shade in the ished thread. The dyestufi, being in a reduced state and in solution, is a constituent of that part of the viscose solution which is recipitated out in the setting bath to form filament-s. The association of the dyestufi with the cellulose compounds of the viscose solution is s0 intimate, that possibly the molecules themselves are affected. Whether the association results in a chemical change or is merely mechanical, the dyestufi' is uniformly distributed throughout the filaments and as the dyestufi becomes oxidized, the filaments are thoroughly impregnated with the desired color without regard to their size. Also, inasmuch as the color has been finally fixed in the filament, any subsequent change of the fiber from hydrocellulose to oxycellulose will not result in any change in the color which has been originally produced.

A further advantage of the method herein disclosed of producing dyed rayon thread rests in the fact that all of the dyestufi' put into the solution is apparently taken up by the viscose. Consequently there is no waste of the dyestufl' such as is found in the usual The dye in paste form is then methods" of handling vat dyes where the skeins or hanks of rayon when submerged in a dye bath take up only a portion of the dye in the solution. Furthermore, since it is known that all of the dyestufi' will be taken up by the preci itated viscose in even ."oportion, it is possi le by measuring the yestufi and other ingredients used in making the viscose solution, to determine with mathematical accuracy in advance the shade of color which will be produced. i

The nature and objects of the invention having been indicated and the preferred manner of carrying out the invention havin been specifically described, what is claime 1s:

1. The process of producing dyed rayon thread which comprises precipitating cellulose in filament form from a viscose solution while impregnated with dyestuff in a reduced state, and oxidizing the dyestufl to fix the color in the filaments.

2. The process of producing dyed rayon thread WhlCll comprises inserting in the viscose solution a d estufi which may be reduced in an alkaline solution to render it soluble, utilizing the chemical compounds present in the viscose to reduce the dyestufl' and hold it in solution, precipitating filaments from the viscose solution in a setting bath, and utilizing the setting bath to oxidize the dyestufl' in the filaments to produce filaments of the required color.

3. The process of producing dyed rayon thread which comprises inserting in theviscose solution a dyestufi which may be reduced in an alkaline solution to render it soluble, utilizin the chemical compounds present in the viscose to reduce the dyestufi and hold it in solution, precipitating filaments from the viscose solution in a setting bath, and oxidizing the dyestufi' in the filaments to produce filaments of the required color.

4. The process of producing rayon thread which comprises inserting an indanthrene dyestuff in the viscose solution, holding the dyestufi in a reduced state in the solution, precipitating filaments from the viscose in a setting bath, and oxidizing the dyestufl' to fix the color in the filaments.-

5. The process of producing dyed rayon thread which comprises adding a dyestufi which may be reduced in an alkaline solution to render it soluble to cellulose zanthate and a three percent caustic solution, thoroughly mixing the dyestufi' with the solution to reduce the dyestufi and hold it in a reduced state, precipitating cellulose in the form of filaments from the viscose solution in a setting bath, and oxidizing the dyestufi' to fix the color in the filaments.

6. The process of producing ra on thread which comprises inserting a dye o the oup consisting of sulphur dyes and indant rene or vat dyes in the viscose solution, holding the dyestufi in a. reduced state in the solution, precipitating filaments from the viscose in a setting bath, and oxidizing the dyestufi' to fix the color in the filaments.

In testimony whereof I have signed my name to this s c-ification.

G ORGE R. LOCKHART. 

